fibrous vs globular proteins

• globular proteins - Proteins with complex tertiary and sometimes quaternary structures

  Compact and water soluble - this is as a result of hydrophobic and hydrophilic interactions of the R groups. Globular proteins are very important for chemical reactions, muscle contractions etc

  
• haemoglobin - Used to carry oxygen round the body in the blood.

  made up of 574 amino acids

  arranged in 4 subunits

  held together by disulphide bonds

  each chain also contains a haem group (contains iron). this binds to / releases oxygen

  
• Conjugated proteins are globular proteins with a non-protein component called a prosthetic group. (proteins without these groups are known as simple proteins)
• Fibrous proteins are insoluble, long molecules.

  Proteins with little or no tertiary structure causing them to form long parallel chains with occasional cross linkages forming fibres. They are used in connective tissue in tendons

  
• This is a fibrous protein- Keratin

  
• This is a globular protein- Amylase

  
• This is a globular protein- Haemoglobin

  
• This is a fibrous protein- Collagen

  
• insulin -

  • globular
  • tertiary structure
  • hormone for blood glucose regulation
  • structure allows solubility - needed for hormones
• haemoglobin -

  • globular
  • quaternary structure with haem groups
  • transport of oxygen around the body
  • conjugated - haem group - these are protected
• catalase -

  • globular
  • quaternary structure
  • catalyse reactions prevents +++ H2O2
  • the prosthetic groups allow interactions H2O2
• keratin -

  • fibrous
  • long chains of repetitive amino acids
  • hair, skin ,nails
  • strong disulphide bridges determine flexibility
• elastin -

  • fibrous
  • quaternary protein with tropoelastin
  • blood vessles / alveoli flexibility
  • found in elastic fibres to give flexibility
• collagen -

  • fibrous
  • 3 polypeptides wound together in a rope
  • connective tissue
  • winding of structure results in long and strong properties